The Pathology Core will play a key role in the Nathan Shock Aging Center. Age-related pathology increases exponentially with advancing age and is largely responsible for age-related morbidity as well s mortality. Knowledge of the pathological lesions associated with various interventions that will be utilized by the Center to study aging is essential to interpreting the impact of those interventions on the aging process(es). This knowledge would also provide insight into the underlying mechanism of the interventions. Pathological assessment of old animals that re included in basic studies of biological aging processes is equally important to help determine whether changes observed as animals age are associated with or independent of underlying pathological conditions. It is, therefore, essential to obtain accurate and thorough pathological assessments of aging animals. The Pathology Core described herein will build on the extensive experience that the Core Leader has had with establishing a pathological component in a Program Project. The specific aims of the Pathology Core in the Nathan Shock Aging Center are as follows: 1. To provide comprehensive pathological analyses of the established as well as new rodent models of aging developed in the Transgenic Core and maintained by the Animal Core. 2. To assist faculty in the pathological analysis of aging animals whose tissues, cells, or molecular mechanisms are aging studied. 3. To advise faculty and students interested in aging of the value of and special requirements for pathological assessment of aging animals.